Conventional prior art shoes have been designed and constructed according to trends, with emphasis on cosmetic appearances rather than upon the bio-mechanical requirements of the anatomy involved. Heretofore, Orthotic control devices have been restricted to individual problems, but without an overall treatment of the many small but significant factors which are present within every individual's foot and having an effect upon his health and well being. That is, posture as it is effected by footwear has significant influence over pathologic difficulties with the anatomy, involving the bones, ligaments, cartilage, muscles, and general disposition of the internal organs. The problem lies in the sole of the shoe, including its attachment to the shoe upper, and tread design and frictional qualities thereof are not the answer. It is the basic foot-form or "last" which is of concern, to which linearly unyielding soles have been attached. And, since the sole controls the manner in which the entire shoe reacts to the usually hard unyielding ground surface, it is a general object of this invention to provide an Orthotically dynamic last and sole construction that compensates for ground surface hardness and irregularities while applying natural forces directly through the anatomy of the ankle processes.
The Orthopedist or Podiatrist works with many variables in specifying corrective control devices built specifically to control particular problems. However, it is the conventional shoe last and dynamic sole functions with which the expert must deal in his substitution of or insertion of corrective devices. For example, formed arch inlays superimposed upon a conventional linearly unyielding sole; this being a comforting factor but limited in the capacity of controlling the forceful leverages created continuously with every step. It is an object of this invention therefore, not to merely change existing last and sole design but to provide a new and improved last and sole which applies bio-mechanical effects as they compliment the anatomy through the ankle and leg processes.
The present invention involves the stabilizing of the ankle processes, it being a general object to do so, and particularly the sub-talar joint from which the calcaneus extends, and the mid-tarsal joint from which the remainder of the foot extends. With the present invention there is protection which inherently stabilizes the foot so as to protect against fatigue and so as to prevent violent pronation or supination otherwise likely to cause stress and/or injury. As used herein: pronation is "a flattening of the long arch (medial arch) or a motion which everts the sole (plantar aspect) of the foot", and supination is "a motion of the foot which inverts the sole thereof" or "to turn the foot inwardly".
The dynamics of a gait or stride cycle varies from person to person, but invariably involves the "strike" of the foot with the ground support or playing surface, the "slap" of the heel as the sole flattens at the heel, the "pronation" as the plantar surface of the foot faces the playing surface for support, and supination as the foot moves towards propulsion and "toe-off" and leaves the playing surface. Accordingly, it is an object of this invention to accommodate the aforesaid dynamic functions by catching the heel at the strike and to stabilize the foot processes throughout the following dynamic functions of slap, pronation, supination and toe-off. More specifically, the foot processes are stabilized or balanced by a neutral sub-talar joint and a locked mid-tarsal joint in a cup of the dynamic last or sole. In practice, the sole has a calculated amount of distortion patterned so as to react under pressure and to yield to the force of the strike and to absorb the impact of the slap. Said distortion increases proportionately with increased loadings.
The material of which a shoe is made, particularly the sole, not only determines the shape but also the action thereof--stiffness or flexibility. It is an object of this invention to not only select materials conducive to the function provided for but also to fabricate the materials in a manner to enhance and/or supply the bio-mechanical functions herein prescribed. To these ends therefore, there is provided an elastomeric solid or the like using a system of varied thicknesses for resilience and the establishment of beam and rib support; or a system of non-interconnected and interconnected gas filled cells, as for example by using layers of flexible material selectively joined and bonded together so as to check the flow of gases captured thereby and so as to control the distortion related to both cushioning and flexibility.
TECHNICAL ANALOGIES for an understanding of the concepts herein disclosed are as follows:
The reason for a shoe, or sole, is to protect the foot from the various playing surfaces and to give the best possible traction and friction qualities between the foot and said surface; as by using a variety of materials, sole tread patterns, spikes, cleats and so on. For example, a shoe is not necessary at all, for even the most aggressive activity, when the playing surface is loose soft sand. The finer and firmer the sand becomes, until eventually hard as concrete (see FIG. 4), the greater the need for compensating systems that the individual must attach to the feet to protect and isolate the feet from the playing surface. When the playing surface is loose soft sand, the lower ankle or sub-talar joint and mid-tarsal joint, or transverse tarsal joints, of a stable foot, can maintain their braced neutral attitude and structural integrity, and the strike or impact forces are dispersed directly through a "locked and rigid" foot and into the sand long enough for the muscles to balance and brace the ankle processes. In other words, the soft sand allows an individual to easily control and maintain both the rearfoot and forefoot stability perpendicular to the forces transmitted through the tibial shaft. This is because the sand acts as a natural shock absorber distributing the strike loadings of each stride over a long time period so that the foot has time to be balanced by supporting muscle contractions while the shock loadings are dissipated into the sand. The individual can also maintain the pre-strike attitude of the sub-talar joint in neutral and the mid-tarsal joint locked throughout the entire gait phase. Thus, the foot remains a balanced and rigid lever for stability and propulsion. With the sub-talar joint neutral and the mid-tarsal joint locked the loadings are transmitted directly through the foot without being lost in an otherwise very complex system of collapsing bones and compensatory motions. In this way the participant can support much higher loadings, because the foundation is more stable and a mechanically efficient structure, the participant being better balanced with much less risk of injury and provided with a much higher performance capability.
As the sand becomes harder, until eventually as hard as concrete, more of the strike forces have to be absorbed and compensated for. The sub-talar (ankle) system is not always strong enough to resist an impact loading of reduced time duration, in which case it may not be possible to bear forces evenly throughout the foot or inside edge of the foot overloaded and unbalanced and subject to severe supination or pronation. Therefore, this shoe is provided so that the strike forces are transmitted as directly as possible to the playing surface, through a neutral sub-talar joint and a locked or muscularly well supported mid-tarsal joint, with an energy absorbing system that varies beneath the different plantar portions of the foot. In other words, this shoe is a dynamic Orthotic device that adapts to the foot in a carefully controlled manner, at the moment of strike when the weight bearing loads are the greatest, creating a "catch" or cupping shape to capture the heel and stabilize it, blocking any tendency for the sub-talar joint to move out of neutral or the mid-tarsal joint to unlock, this shoe stabilizing the lower ankle and foot in neutral, balancing the foot against typical pronation, and controlling the carriage of weight throughout every phase of gait from standing to running and jumping.
Concerning the heel aspects of the shoe, the strain loadings can be very high and of short duration during strike contact, at which moment shock absorption and the dissipation of force is most important. It is the time when the foot articulation processes is most susceptible to being overloaded, tending to slip or distort and causing pronation in most people, limiting their performance potential and comfort. The purpose of this shoe is to capture or "catch" the heel at neutral, just as it is the moment before strike contact, by yielding in such a way as to hold the ankle and foot system at neutral and locked until the stress loadings have been dissipated. The physical properties of the materials determines the exact profiles and configuration of the sole with respect to the calcaneus, as will be described. For example, a material having a determined slow rate of memory can be employed, so that after each strike the shoe will be slowly released at a predetermined rate from its distorted configuration and act as an Orthotic device through dynamic weight bearing, there being a limit to such distortion so that the sub-talar joint and mid-tarsal joint will remain stabilized. Accordingly, the shoe distorts to absorb the strike forces with every landing, and when the forces dissipate the heel cup returns to neutral, supporting the heel weight in a springy fashion throughout the remainder of the gait cycle, or while the individual is standing. In this way the shoe is totally dynamic, always adapting to the weight loadings which are directly related to the tendency for the feet to distort or pronate.
The following percentage sequence of the gait cycle is shown in FIG. 3 of the drawings, the basic functions of the shoe heel being as follows:
At 0% just before strike the sub-talar joint is neutral, the mid-tarsal joint is locked, and both are braced and ready to absorb the impact.
At 10% just after the strike the heel catching mechanism distorts in a predetermined manner to catch or cup the heel and to hold the sub-talar system neutral and locked, while at the same time tempering or dissipating the stresses of impact. Note that this first heel contact is typical of a walking gait, and that this "catch" function of the shoe also applies in running when the strike is first made on the forefoot followed by impact applied to the heel.
At 25% the lively action of the heel cup tempers and dissipates the impact and loading forces much like a spring while the forefoot plantar surfaces begin making contact with the ground.
At 50% the entire plantar portion of the foot is in contact with the ground as the weight moves forward about midfoot. The heel of the shoe remains active in tempering the weight of the individual and forces him from the ground, while the other parts of the shoe are performing their controlling functions. At this point the shoe functions are as if the individual were to strike at midfoot, or forefoot or to be simply standing.
At 95% the plantar surface of the shoe is raised and readied for toe-off. It is important to note that throughout the whole gait cycle the sub-talar system has remained neutral.
This shoe has little or no distortion while standing, depending for example upon the weight being borne by the shoe and how the individual bears weight between the feet, i.e. more weight upon one foot than the other, weight of the individual being a variable that is coordinated with the flex modulus of the materials used and complemented by the sole configuration.
As shown in FIG. 7, "slap" is very apt to occur in ordinary shoes right after heel strike which often initiates a very powerful lever system that tends to flatten the sole onto the usually hard and flat playing surface with a violent slapping action. This slap is a stress that is transferred directly to the anatomy, wrenching and tending to dislocate the original braced and neutral posture of the foot before strike. It is often a stress too great for the anatomy to resist, and is transferred from pronation to tibial rotations, hips and on through the remainder of the anatomy. Dislocations therefrom result in a hypermobility of the foot throughout the whole gait phase, also creating an inefficient lever system for the foot to propel from, and the excessive motion and mobility accelerates fatigue and inefficiency in the transmission of forces between the individual and the surface.